Final Monitor controller sends A320 on missed approach as it is less than the 8 miles required behind a preceeding A380.

Narrative

Air Carrier X; an A380; was on the ILS approach at about a 4 mile final and on my frequency. Final sequenced Air Carrier Y; an A320; behind Air Carrier X and turned him onto final less than the required 8 Miles in trail required; as per FAA Directives. As Final switched Air Carrier Y onto my frequency; I canceled Air Carrier Y's approach clearance; had him maintain 2000 FT and track the localizer. It appeared to me that this allowed for vertical separation and was my first opportunity to affect a safety measure in this instance. The A380 usually lands here at non-busy times. However; this time it was in the middle of rush of traffic and made the degree of difficulty a bit too much. Lower the required separation standards behind the A380 to a more reasonable level or enact flow measures when this aircraft comes in that really address the problem. The typical flow measures now are such that the controllers working the aircraft in do not see any effect from them. It just gets busier when the A380 lands because the capacity of the airport is decreased by 2-3 aircraft for that 10 minute time frame. That transfers into a 30% reduction in capacity for that period. That is NEVER addressed. They look at hourly numbers as indicative only.